Soluble guanylyl cyclase (sGC) is one of the crucial enzymes in the NO-cyclic GMP (cGMP) signaling cascade involved in smooth muscle relaxation, inhibition of platelet aggregation, and neurotransmission. sGC is the target of various pharmacological compounds currently used for treatment of cardiovascular disorders. However, the mechanisms governing stimulation of activity or expression of sGC are poorly understood. Effective manipulation of sGC-dependent synthesis of cGMP for therapeutic purposes requires understanding of the pathways involved in regulation of sGC levels and activity. The goal of this proposal is to determine the molecular mechanism of enzyme activation by alisoteric effectors including development of approaches for NO-independent regulation of sGC, investigation of the mechanisms regulating sGC expression, and analysis of the effects of short-term and long-term modulation of sGC activity and expression on cell physiology. To achieve this goal, a constitutively activated sGC mutant will be expressed in a cell model providing for elevated levels of cGMP, whereas expression of domains involved in formation of functional heterodimers of sGC will result in decreased enzyme levels and lowered NO-dependent synthesis of cGMP. The promoter fragments of sGC genes will be identified and characterized as well as the mechanisms of post-transcriptional regulation of sGC Human cell culture models will be developed and the effects of short-term and long-term sGC regulation on cell physiology will be determined. The knowledge of the mechanism of sGC regulation will advance our understanding of the role of sGC/cGMP system in various biological processes.